Gammill was arrested earlier this month on multiple charges, including dependent adult abuse, furnishing dangerous drugs without a license and practicing medicine without a license.

Officials say they found 25,000 prescription pills at the treatment center at his home, including morphine, Ambien, steroids and other drugs of Mexican and Russian origin. The investigation started after a patient came to police with her concerns, authorities say.

The female patient, asking ABC News not to use her last name, identified herself as Fern and said she paid Gammill $2,000 for two days of treatment. She told ABC News that she was given mysterious powder and oil that were mixed in a capsule, which matches what the alleged victim told authorities, according to a police report.

"She began to get a burning sensation in her stomach and Gammill told the victim it was good her stomach was burning because that meant the ingredients were still active," the police said.

Gammill is out of jail on $10,000 bail and is scheduled to make his first court appearance Aug. 31, according to court records. Officials say they are investigating whether other people have had any issues with Gammill.

Gammill did not respond to ABC News requests for comment. Police said they have no evidence that he has any medical training.

Fern said she had followed Gammill's work online since 2008 when she was first diagnosed with breast cancer. After the cancer spread to her brain, lungs and bones, she was more willing to try his treatments, she added.

"[Cancer patients are ] very vulnerable because there isn’t a cure and when you’re getting further down the line you get desperate," she said.

She said she is not aware of any adverse effects from the substances Gammill allegedly gave her.

Fern said she traveled about 300 miles from her home in Northern California to see Gammill for two days. She said she was disappointed the first day when Gammill appeared to not have looked at her medical history. The second day made her even more skeptical after seeing his version of treatments, so she said she eventually sought out police after some of his statements did not make sense to her.

"I was very upset that there was somebody who was preying on cancer victims," she told ABC station KABC-TV in Los Angeles.

Gammill's website for his "Natural Oncology Institute" remained online as of Friday, where he describes starting the center because, "he wanted to create a non-profit where cancer patients could get a [sic] honest answers from someone who knew both conventional and alternative medicine and could give honest answers without sizing up their wallet.”